1. Field of the Invention
The present invention generally relates to cooling apparatus using boiling refrigerant, and more particularly to a cooling apparatus using boiling and condensing refrigerant which cools a heating element, such as heated semiconductor element.
2. Description of the Related Art
As a conventional apparatus for cooling semiconductor elements which generate heat while being driven, there has been a technique disclosed in the Japanese Examined Patent Publication No. 3-29181, for example. This technique is embodied as a hermetic siphon system in which the heat generated by a semiconductor element is absorbed by refrigerant, thereby the refrigerant is gasified and rises through a radiation part, then the heat is radiated to the outside from the radiation part, and in this way the semiconductor element is cooled.
In such apparatus, inner fins vertically laid out within the radiation part is formed so that the heat emitted from the refrigerant can easily be absorbed by the radiation part.
However, according to the apparatus disclosed in the Japanese Examined Patent Publication No. 3-29181, as the boiled and gasified vapor rising flow and the condensed and liquefied return flow run reverse, these flows turn into the what is called flushed state as the vapor velocity increases. This makes the liquid flow impossible to further return, and poses a problem that the maximum heat transportation rate is lowered.
Another technique has been disclosed in the Japanese Patent Application Laid-Open No. 57-204156, in which a passage is formed for passing therethrough the boiled and gasified refrigerant and a passage is formed for passing therethrough the condensed and liquefied refrigerant within the radiation part. According to this technique, inner fins are formed at vertically uniform intervals within the radiation part and a special sheet member is arranged at the under part of the inner fins to actively guide the boiled and gasified refrigerant into any of the inner fins. This publication also carries a statement that a plurality of special pipes are arranged outside the radiation part for use as passages for passing therethrough the boiled and gasified refrigerant and as passages for passing therethrough the condensed and liquefied refrigerant.
However, according to the technique disclosed in the Japanese Patent Application Laid-Open No. 57-204156, the special sheet member is disposed at the under part of the inner fins to actively guide the boiled and gasified refrigerant into any of the inner fins. This poses a problem that not only additional man-hour would be required for installation of such special sheet member but also, as the inner fins into which the boiled and gasified refrigerant is guided are constructed to comparatively be narrow, efficient cooling can not be achieved.